A process transmitter for measuring a process variable in an industrial process comprises a sensor module, a heating device and transmitter circuitry. This formulation exhibits significant advantages over the sustained release valproate formulations of the prior art. In one embodiment, this composition may be used as a product for caring for andor making up keratinous substances, for example, the skin, lips, andor superficial body growths. The BaF2 and the ZnSe films formed on said BaF2 film are formed on the main surface of the optical substrate, which has been smoothed, by Xe gas ion assisted vapor deposition.